1. Field of the Invention
The present invention relates to an implantable penile prostheses, and more particularly to an extendable penile prosthesis.
2. Description of Related Art
Penile prosthesis are typically implanted into a patient to overcome erectile impotence. Most penile prosthesis have inflatable cylinders that are surgically implanted into the corpora cavernosa regions of the penis. The cylinders are typically connected to a pump that transfers fluid from a reservoir to the cylinders.
Prior penile prosthesis include the devices described and shown in U.S. Pat. No. 4,009,711 issued to Uson, U.S. Pat. No. 3,954,102 issued to Buuck, U.S. Pat. No. 4,235,227 issued to Yamanaka and U.S. Pat. No. 4,726,360 issued to Trick et al, which disclose simple inflatable tube-like cylinders that expand when pumped with a working fluid. The cylinders are typically constructed from a nondistensible material and are blown up in the same manner as the inner tube of a tire. Unfortunately, these devices do not provide much lengthwise expansion of the penis, which is part of the natural movement of a normal penis during erection.
U.S. Pat. No. 4,730,607 issued to Fischell and U.S. Pat. No. 4,718,410 issued to Hakky, disclose an inflatable cylinder having bellows which provides significant elongation of the prosthesis and consequently, of the penis, when inflated. However, there is a problem with the retraction of the bellows in these devices after use because the rate of retraction is dependent only upon the memory of the bellows material such that the spring rate of the bellows is low. Therefore, the cylinder of these devices does not readily contract when the operating fluid is removed from the penis pendulus area of the implant. Such a prosthesis may require manual manipulation to fully return the penis into a natural flaccid position. Therefore it would be desirable to have an inflatable penile prosthesis cylinder that provides considerable lengthwise expansion and readily contracts into a natural flaccid position.